Noise generated by an aircraft when taking off stems principally from its jet engine and the “jet” flowing out of it. This is particularly true for aircraft whose jet engines do not have very high dilution levels, as is notably the case with supersonic transport aircraft. In the case of military aircraft, vectorization is sought to augment the lateral or vertical efforts. Augmentation of lift in civil transport can also be envisaged to reduce, e.g., take-off distances.
Known in the prior art are passive methods consisting of a modification of the geometry of the lip of the jet to be manipulated. These devices, such as lobe mixers and miniature flaps, are nevertheless very difficult to add to and remove from a variable cycle engine.
Among the active mixing control methods suitable for supersonic jets, there are pneumatic or mechanical actuators. However, since the region of maximal receptivity is located at the discharge lip of the jet, the characteristic scales of flow are therefore very small and at very high frequencies. These constraints, added to the fact that the area involved is difficult to access in the case of commercial aircraft jet engines, make such jet control devices poorly suitable for in situ installation.
Also known in the prior art is a nozzle cut in a zigzag manner which is intended to mix the hot flux and the cold flux to reduce noise. Although such a system has the advantage of not increasing the weight of the engine, it nevertheless has the drawback of not adapting to different operating regimes or modes (vectorization, infrared signature, noise).
It would therefore be advantageous to resolve these drawbacks of the prior art by providing a device for controlling thee mixing of the jets by controlling separation of the primary jet generated by abrupt divergence of the walls of the nozzle, thereby using control of the separations as a method for excitation of the mixing layers.